If Lysychansk falls, the entire region of Luhansk – which together with Donetsk makes up the eastern Donbas region – could come under Russian control, marking another strategic breakthrough for Vladimir Putin. Andrei Marochko, a spokesman for the Russian-backed forces, told Russian state news agency Tass: “Today the Luhansk People’s Militia and Russian forces captured the last strategic heights, which allows us to confirm that Lysychansk is completely surrounded ». The Guardian was unable to independently verify the claims. On Saturday, Ruslan Muzychuk, a spokesman for Ukraine’s national guard, told Ukrainian television that although of all fronts, “the situation in Lysychansk was the most difficult, the city itself is not surrounded and is controlled by Ukrainian forces.” . After destroying its twin city of Sievierodonetsk last week, Lysychansk has become the new focus of fighting in eastern Ukraine. It has been under constant shelling and airstrikes by Russian artillery for weeks. “Private houses in the attacked villages are burning one by one,” Serhiy Haidai, governor of the Luhansk region, wrote on the Telegram messaging app on Saturday. “With such a high density of shelling, we only have time to protect the wounded. Fires at the same time in many places. We barely have time to put out the large-scale fires in Lysychansk.” According to accounts, the occupiers are destroying one house after another with heavy artillery, with residents hiding in basements almost around the clock. The Russian Defense Ministry said its forces had taken control of an oil refinery on the edge of Lysychansk in recent days, but Haidai reported on Friday that fighting at the facility continued. Subscribe to First Edition, our free daily newsletter – every morning at 7am. BST In a separate development, a series of powerful explosions rocked the southern Ukrainian city of Mykolaiv in the early hours of Saturday. “There are powerful explosions in the city! Stay in shelters!’ Mykolayiv mayor Oleksandr Senkevych wrote on Telegram. Before the explosions, air raid sirens sounded across the Mykolaiv region, where on Friday, according to Vitaly Kim, head of the Mykolaiv regional military command, another 12 Russian missiles were fired, most of which were intercepted by Ukrainian forces. The cause of the explosions was not immediately clear, although Russia said on Saturday that they hit army command posts in the region. “Russian forces destroyed five Ukrainian army command posts in the Donbass and Mykolayiv region with high-precision weapons,” the Russian Defense Ministry announced on Saturday. At the start of the invasion, Russian troops had practically surrounded Mykolaiv and its port on the Bug River. Moscow troops had seized its airfield and were advancing from the northeast. However, after weeks of fighting, the Ukrainian army managed to push back the Russians. Since then, and in recent months, Mykolaiv, which together with its charismatic commander, has become a symbol of the country’s resistance, the fighting has turned into a “rocket and artillery war.” According to Ukrainian authorities, Mykolaiv, which borders the vital port of Odessa, is seen by Moscow as a strategic target in order to achieve its goal of annexing Ukraine’s Black Sea coast, making Ukraine a “non-maritime country”. On Friday, at least 21 people, including two children, were killed when two Russian missiles hit a high-rise apartment building and a leisure center in buildings in the town of Serhiyivka, near Odessa. The video shows the charred ruins of buildings. The Ukrainian president’s office said three X-22 missiles fired by Russian warplanes hit an apartment building and a campsite shortly before 01:00 local time. Ukraine’s security service said another 38 people, including six children and a pregnant woman, were taken to hospital with injuries. Most of the dead and injured were sleeping when the rockets hit. The attack came at the end of a week in which Moscow has stepped up long-range attacks, hitting civilian targets far from the front lines. Ukraine’s attorney general, Iryna Venediktova, said investigators were recovering missile fragments and taking measurements to determine the trajectory of the weapons. “We are taking all the necessary investigative measures to identify the specific people who are guilty of this terrible war crime,” Venediktova said. Ukrainian authorities interpreted the attack as retaliation for Russian troops being forced off the strategically important Snake Island a day earlier. “The occupiers cannot win on the battlefield, so they resort to brutal killings of civilians,” Ivan Bakanov, head of Ukraine’s security service, SBU, said of Friday’s attack. “After the enemy was displaced from Snake Island, he decided to respond by cynically bombing civilian targets.” Russia presented the withdrawal from Snake Island as a “gesture of goodwill”. Ukraine’s military said the Russians fled in two speedboats after a barrage of Ukrainian artillery and missile strikes. Kyiv accused Russia on Saturday of dropping incendiary white phosphorus on Snake Island. White phosphorus, known as WP, is a chemical that burns brightly on contact with air, producing dense white acrid smoke and a white light that can be useful for illumination. The high temperature at which it burns also makes it an effective incendiary device in warfare. Ukrainian personnel were not on the island at the time of the attack and, according to military experts, the Russians used it to burn weapons and ammunition left on the island before their retreat.